Nenadic Ivan Z, Qiang Bo, Urban Matthew W, Zhao Heng, Sanchez William, Greenleaf James F, Chen Shigao
Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN, USA.
Phys Med Biol. 2017 Jan 21;62(2):484-500. doi: 10.1088/1361-6560/aa4f6f. Epub 2016 Dec 21.
Ultrasound and magnetic resonance elastography techniques are used to assess mechanical properties of soft tissues. Tissue stiffness is related to various pathologies such as fibrosis, loss of compliance, and cancer. One way to perform elastography is measuring shear wave velocity of propagating waves in tissue induced by intrinsic motion or an external source of vibration, and relating the shear wave velocity to tissue elasticity. All tissues are inherently viscoelastic and ignoring viscosity biases the velocity-based estimates of elasticity and ignores a potentially important parameter of tissue health. We present attenuation measuring ultrasound shearwave elastography (AMUSE), a technique that independently measures both shear wave velocity and attenuation in tissue and therefore allows characterization of viscoelasticity without using a rheological model. The theoretical basis for AMUSE is first derived and validated in finite element simulations. AMUSE is validated against the traditional methods for assessing shear wave velocity (phase gradient) and attenuation (amplitude decay) in tissue mimicking phantoms and excised tissue. The results agreed within one standard deviation. AMUSE was used to measure shear wave velocity and attenuation in 15 transplanted livers in patients with potential acute rejection, and the results were compared with the biopsy findings in a preliminary study. The comparison showed excellent agreement and suggests that AMUSE can be used to separate transplanted livers with acute rejection from livers with no rejection.
超声和磁共振弹性成像技术用于评估软组织的力学特性。组织硬度与多种病理状况相关，如纤维化、顺应性丧失和癌症。进行弹性成像的一种方法是测量由内在运动或外部振动源在组织中传播的波的剪切波速度，并将剪切波速度与组织弹性相关联。所有组织本质上都是粘弹性的，忽略粘性会使基于速度的弹性估计产生偏差，并忽略组织健康的一个潜在重要参数。我们提出了衰减测量超声剪切波弹性成像（AMUSE）技术，该技术可独立测量组织中的剪切波速度和衰减，因此无需使用流变模型即可表征粘弹性。首先在有限元模拟中推导并验证了AMUSE的理论基础。在模拟组织模型和切除组织中，将AMUSE与评估剪切波速度（相位梯度）和衰减（幅度衰减）的传统方法进行了验证。结果在一个标准差内一致。在一项初步研究中，使用AMUSE测量了15例有潜在急性排斥反应患者的移植肝脏中的剪切波速度和衰减，并将结果与活检结果进行了比较。比较结果显示出极好的一致性，表明AMUSE可用于区分有急性排斥反应的移植肝脏和无排斥反应的肝脏。
